The present invention relates to machines for the making of cigarettes, cigars, cigarillos, filter rod sections and analogous rod-shaped smokers' products. More particularly, the invention relates to improvements in the installation and shieldng of components of photoelectric monitoring apparatus in such machines.
It is known to employ photoelectric monitoring apparatus in cigarette making or analogous machines. As a rule, such apparatus comprise a light source or sender and a photosensitive transducer or receiver which latter transmits a signal in response to impingement or interruption of impingement of the light beam issuing from the light source. For example, it is customary to install a detector including a light source and a transducer above the path for discrete cigarettes which slide in a stationary channel between the cutoff and the transfer conveyor of a cigarette making machine wherein the cutoff severs a continuous cigarette rod so that the latter yields a file of discrete cigarettes. The light beam issuing from the source is reflected by the cigarettes and impinges on the transducer whereby the latter produces a signal which can be used for a variety of purposes, e.g., to start the next-following machine of a production line including the cigarette making machine in response to detection of the foremost cigarette subsequent to starting of the cigarette making machine, to arrest the machine or the entire production line in response to detected absence of cigarettes, to start or deactivate one or more units in the cigarette making machine in response to detected presence or absence of cigarettes, and/or many others.
As a rule, photoelectric detectors of the above outlined character are adversely affected by tobacco dust and/or other foreign matter, especially if such foreign matter is allowed to settle on the light source. Any reduction of the intensity of the light beam issuing from the source and/or reduction of the effective area of the photosensitive surface of the transducer as a result of deposition of tobacco dust is likely to affect the accuracy of the monitoring action and can result in premature or delayed stoppage of one or more machines with attendant losses in output.